Several embodiments of light emitting probes designed to be transcutaneously introduced into the body of a patient and positioned at a desired treatment site to administer photodynamic therapy (PDT) using a plurality of light sources are taught in commonly assigned U.S. Pat. No. 5,445,608, the drawings and disclosure of which are specifically incorporated herein by reference. Several different embodiments of such probes are illustrated and discussed il this prior patent. Each of the probes disclosed in this reference includes a plurality of light sources that are mounted on a relatively stiff or inflexible substrate and enclosed within a transparent envelope through which light emitted by the light sources is transmitted to irradiate a tumor or other cells that are to be destroyed by PDT. The light sources used on the probes taught by this reference are preferably light emitting diodes (LEDs); however, almost any light source capable of emitting light in a waveband corresponding to an absorption waveband of a photoreactive agent that has been applied to the tumor or other tissue to be destroyed can be used. By inserting one of these probes into a patient's body, moving the probe to an internal treatment site, and using the probe for applying PDT, abnormal cells or other organisms at the treatment site can be destroyed without significant adverse impact on adjacent normal tissue.
None of the implantable light emitting probes disclosed in the above-referenced patent include light sources mounted on flexible substrates. There are many applications for PDT in which it would be advantageous to use a flexible substrate for mounting the LEDs or other light sources on a probe employed to administer the PDT, e.g., so that the probe can be threaded into a treatment site through a curved passage within the patient's body without risk of perforation of the wall of the passage. In contrast to the relatively inflexible substrate used in the probes disclosed in the above-referenced patent, a flexible PDT probe having a small cross-sectional size, e.g., less than 2 mm, can be more readily maneuvered through body passages using conventional endoscopic techniques, enabling the flexible probe to be inserted to provide a medical therapy, such as the administration of PDT, to a treatment site. In addition, a small cross-sectional area flexible probe is less likely to cause bleeding upon insertion interstitially at a treatment site and become infected after insertion. The prior art does not disclose a flexible probe capable of providing these capabilities.
To address the need for such devices, commonly assigned U.S. patent applications, Ser. No. 08/613,390 filed Mar. 7, 1996, now U.S. Pat. No. 5,800,478, and a continuation-in-part thereof, Ser. No. 08/633,171 filed Apr. 16, 1996, now U.S. Pat. No. 5,766,234, both entitled "Flexible Microcircuits for Internal Light Therapy," disclose several different embodiments of flexible probes. These embodiments include a relatively small diameter, elongate flexible probe. The elongate probe comprises a flexible substrate on which are mounted a plurality of light emitting devices, in a spaced-apart array. The light emitting devices are mounted on each side of the substrate, and are electrically connected to two flexible conductive traces that extend along the surface of each side. The light sources each include terminals disposed on opposite sides of the device. One terminal is electrically connected using solder or a conductive adhesive to one of the two traces. A fly wire (very small gage) couples the other terminal to the other conductive trace. While this arrangement provides a workable flexible probe that is able to bend without damage as the probe is inserted through a small diameter passage, the probe has a larger diameter than desired because the width of the flexible substrate required for this configuration is slightly greater than the sum of the width of the light emitting devices and the width of the two conductive traces. The resulting configuration is also subject to damage when handled before final fabrication of the probe is completed, because the fragile fly wires are exposed until the substrate and mounted light sources are encapsulated in a flexible, optically transparent, biocompatible material. Thus, a more compact arrangement that is more robust and capable of automated fabrication is desirable. Ideally, it should be possible to fabricate a flexible elongate probe having a cross-sectional diameter of less than 0.15 cm, i.e., the width of the substrate should be only slightly greater than the width of the light sources mounted thereon.
It will also be apparent that a flexible probe having a smaller diameter so that it can more readily be introduced to a treatment site has utility for implementing medical therapies other than PDT. For example, a small diameter flexible probe that includes an ultrasonic transmitter and/or ultrasonic receiver can readily be inserted into an organ or through a lumen to carry out an ultrasound scan of surrounding tissue. Furthermore, a small diameter flexible probe that is used to administer PDT can be provided with electronic components capable of carrying out additional functions. For example, a sensor to determine the efficacy of the PDT treatment might be included on the flexible probe, in addition to the plurality of light sources that are used to provide light to a treatment site.
A relatively smaller diameter flexible probe on which one or more electrical circuits for administering a medical treatment or a sensing device is mounted can more readily be threaded into an internal site within a patient's body than a larger diameter probe, and the insertion procedure can be implemented with less trauma to the patient. In addition, a configuration that eliminates use of the fly wires to couple the terminal of a device to a conductive trace should improve the durability of the probe. Producing a smaller diameter probe that is more robust than that of previous designs is clearly a desirable objective.